If $x \triangleright y = 3x-3$ and $x \star y = 3x+y$, find $-2 \triangleright (5 \star 5)$.
Answer: We don't need to find $5 \star 5$ because $x \triangleright y$ depends only on the left operand. Find $-2 \triangleright y$ $ -2 \triangleright y = (3)(-2)-3$ $ \hphantom{-2 \triangleright y} = -9$.